There are tons of comets in our solar system. They usually do not get close to the earth.
The Sun is at the center and is very bright.
A comet is made of ice and rock and has typical size of 10 km in diameter. The largest is 10199 Chariklo at 258 km.
Nasa reports there are 3743 known comets. There is likely billions of them that we do not know about.
Images from NASA:
The next appearance will be in 2061.
The comet’s perihelion (closest approach to the Sun) is only 0.6 AU, and it travels as far from the Sun as beyond the orbit of Neptune. As a result, Halley is not visible from Earth (with naked eyes) when it passes through perihelion.
Comet 103P/Hartley (Hartley 2)
The nucleus of Hartley 2 is estimated to be 3.4 kilometers long, 2.1 kilometers wide and it rotates every 12 hours at the average distance of 2.2 AU from the sun. The coma around its nucleus extends about 20,000 km into space though this could be closer depending on the activity level of the comet’s nucleus. Comet Hartley 2 is moving toward the sun, where it will reach perihelion on November 27, 2010.
Comet Siding Spring Seen Next to Mars
Oort cloud comet C/2014 Q2, aka Lovejoy
Six comet-like tails radiating from a body in the asteroid belt, designated P/2013 P5
Comet Siding Spring
Hubble View of ISON
Composite photo, images of Jupiter and Comet P/Shoemaker-Levy 9
They are fast moving. Example speeds:
Borisov 175,000 km per hour
Neowise 230,000 km an hour
Leonard 254,400 km per hour
The time it takes to travel one orbit is the period, here are examples from NASA data:
Halley 76.1 yrs.
Encke 3.30 yrs.
d’Arrest 6.51 yrs.
Tempel 1 5.51 yrs.
Borrelly 6.86 yrs.
Giacobini-Zinner 6.52 yrs.
Grigg-Skjellerup 5.09 yrs.
Crommelin 27.89 yrs.
Honda-Mrkos-Pajdusakova 5.29 yrs.
Wirtanen 5.46 yrs.
Tempel-Tuttle 32.92 yrs.
Churyumov-Gerasimenko 6.57 yrs.
Schwassmann-Wachmann 3 5.36 yrs.
Kohoutek 6.24 yrs.
West-Kohoutek-Ikemura 6.46 yrs.
Wild 2 6.39 yrs
Chiron 50.7 yrs.
Wilson-Harrington 4.29 yrs.
Hale-Bopp 4000. yrs.
Hyakutake 40000. yrs.
Pictures of comets:
More cool pictures of comets: